The Pentagon said on Sunday the United States was filing a complaint to Russia through diplomatic channels after an intercept of a US reconnaissance plane by a Russian fighter jet last week, calling it an aggressive operation by Moscow.

"Unprofessional air intercepts have the potential to cause harm to all aircrews involved," said Pentagon spokesman Army Colonel Steve Warren in a statement. "More importantly, the careless and unprofessional actions of a single pilot have the potential to escalate tensions between countries."

According to the Pentagon, a US RC-135U, a reconnaissance plane was flying in international airspace over the Baltic Sea north of Poland when a Russian SU-27 fighter intercepted the US aircraft using "unsafe and unprofessional maneuvers" in close proximity.

The encounter took place on Tuesday and was only publicly discussed by the Pentagon in recent days.

Meanwhile, Russian Defense Ministry on Saturday dismissed the US claim, saying the incident happened when the Russian fighter on duty spotted an unknown target over the Baltic Sea that was moving toward the Russian border.

"As to the judgement about the professionalism of Russian pilots, this is up to the Russian side, and the US reconnaissance aircraft can only perform routine fights near the US borders," said Russian Defense Ministry spokesman Igor Konashenkov.